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Mapping and Monitoring of Metamasius callizona and Its Host Plants in
South Florida: January 2001 - December 2001
An exotic weevil, Metamasius callizona, has spread across south Florida and has been decimating native
bromeliad populations, particularly Tillandsia utriculata and T. fasciculata. Dr. Howard Frank of the Entomology
and Nematology Department at the University of Florida has been working on a classical biological control solution.
In January 2001, a multi-tiered method for mapping and monitoring the weevil and its host plants was developed
and implemented in Myakka River State Park in Sarasota County Florida. A baseline population of hostplants is
being monitored. Weevils found in mapped areas are being counted. This information, in relation to seasonal
and ecological factors, will be used to determine optimal time and location for release of a biological control agent.
As well, this information will indicate the rate of mortality being suffered by the host plants due to the weevil
and which host plants are most susceptible. Monitoring will continue after the release of a biological control agent.
Mapping and monitoring of the weevil, Metamasius callizona Chevrolat, and its host plants, Tillandsia
fasciculata Swartz and T. utriculata Linnaeus, have been ongoing in Myakka River State Park in Sarasota
County Florida since January 2001. This research will aid in the biological control efforts (Larson, 2002)
being promoted by Dr. Howard Frank of the Entomology and Nematology Department at the University of Florida.
M. callizona is a pest weevil (Larson, 2002) that has been causing substantial damage to bromeliad populations
in south Florida (Frank and Thomas, 1994). Besides the bromeliad species mentioned, other genera
potentially affected include Catopsis and Guzmania; for a list of species affected, see Florida's Native
Bromeliads Illustrated (Frank, 2000).
This research is an ecological population study from which a data-analysis system is being developed to describe
the interactions between M. callizona and its host plants. Method development occurred between January 2001
and May 2001. Implementation and further development has been ongoing. A baseline description is being
developed for further refinement of system parameters and for detailing analytical strategy.
Parameters used in a data-analysis system depend on habitat of study, organisms involved and focus of
research (Kingsland, 1985). Weevil-host plant habitat is the range of the host plant. Range varies depending on
the frost line (host plants do not tolerate freeze); present host plant range is south Florida (see
http://savebromeliads.ifas.ufl.edu/distribution.htm Distribution by County of Native Bromeliads in Florida
(Larson, 2002)). The weevil-host plant system is multi-tiered. South Florida is the first tier.
Host plants are usually found in habitats that support oak growth, along river systems. (Myers and Ewel, 1990).
Tier II is made up of the drainage basins in south Florida, according to the Florida Atlas, 1992. One drainage basin
is in the system: Myakka River Drainage Basin.
Tier IIIs are large stretches of land with fragmented tree populations that support host plant growth. One Tier III is
in the system: http://www.myakka.sarasota.fl.us/ Myakka River State Park (MRSP). The fragmented tree
populations are Tier IVs. For a list of Tier IVs (names and acronyms) and a map showing their relative
positioning, see MRSP MAP. HPA density defines Tier IVs (10-100 HPA/TIV). An HPA (Host Plant Area) is the host
to the host plant. Tier IV examples: CGNRP (high end) and SPA (low end).
Tier IVs are divided into Sections, 3-10 HPAs/Section. (For a complete outline of the method, see Method.)
Examples: CGNRP:Section-4 and SPA:Section-2.
Host Plant Areas in randomly selected Sections are mapped. Examples: CGNRP:Sect-4:HPA-7 and SPA:Sect-2:HPA-
3. Photographs are taken of the host plants when they enter the system. Examples: CGNRP:Sect-4:HPA-7:hp049
Monthly collection trips are made to monitor Sections, HPAs and host plants. A collection schedule may be found
at Collecting Schedule.
Size of host plant, size of host plant patch, host plant density within a patch, and whether or not the patch exists as
a monoculture or polyculture can strongly affect the behavior of a plant-eating insect. (Strong et al, 1984).
Host plants in MRSP share the canopy with other epiphytes, including three species of Tillandsia, T.
usneoides Linnaeus, T. setacea Swartz and T. recurvata Linnaeus; resurrection fern (Polypodium
polypodioides Linnaeus); and the orchid Encyclia tampensis Lindley (Myers and Ewel, 1990). Are the weevils
attracted to large, dense host plant populations, or individual, isolated host plants? Are they prone to discover
host plant populations composed solely of host plants, or host plants in mixed populations? Or might neither or
a combination of density and plant mix affect weevil behavior?
Natural enemies are the primary density-dependent population regulators of phytophagous insects (Strong et
al, 1984). The weevil lacks natural enemies in south Florida (Frank, 1994). Management using biological control
re-introduces a natural enemy (Larson, 2002). A fly (Admontia sp.) is presently being studied for host specificity
and rearability (Larson, 2002). When this agent, or some agent, is available for release, mapping and
monitoring efforts will help determine the most efficient application of the agent to the field. Also, post-
release monitoring can be compared with pre-release monitoring.
A biological invasion may progress in a series of microepidemics characterized by resource depletion of a
localized host plant patch, followed by dispersion, resettlement and depletion; this cycle continues
(Hengeveld, 1989). Host plant patches in four TIVs (FLRE, SPR, NPR and CWW) in MRSP are being depleted by
the weevil. History of Metamasius callizona offers examples of other sites in south Florida that have been
decimated (Frank, 2000). Understanding how the weevil disperses will help determine where a biological
control agent should be released.
Other factors affecting the weevil-host plant system include climate and weather. Climate in south Florida
is characterized by distinct wet/dry seasons, and seasonal hurricanes and tropical storms (Winsberg, 1990).
Host plants in the field have shown susceptibility to freezes, wind, flood, drought and excessive heat. Rates of
non-weevil modes of mortality suffered by host plants may be compared to the degree of mortality caused by
the weevil to understand how badly the weevil is hurting the host plant populations.
DATA AND ANALYSIS
Measures Data are being stored and manipulated at the Mapping and Monitoring Web site I maintain. This Web site
is in a perpetual state of creation and tables and graphs are being regularly updated. The following categories
of information have been sorted from the collected data:
Sections, HPAs and host plants in MRSP (Graph MRSP-1) and in Tier IVs (Graph 01). These graphs monitor
the number of tiers and host plants that exist in the system.
HPA type and number for MRSP may be found in Table MRSP-1 and the HPA type, number and status over time
for Tier IVs may be found in Table 05. HPAs that have been described include oaks (predominantly);
other hardwoods; pine trees; sabal palms; vines; fallen branches; ground. Areas with more pine trees, such
as CGNRP, have more pine HPAs; areas with more sabal palms, such as CWW, have more HPAs that are sabal palms.
Graph MRSP-2 shows size distribution of the host plant population in MRSP. Fifty percent of the population is
small; 25% medium and 25% large. Pre-weevil size distribution is unknown. Locals claim the woods were
once teeming with large bromeliads.
Graph 02 shows host plant size distribution for Tier IVs. HC, CGNRP, CGPA, and FHR have populations greater
than 50% small. CGR, FLRE, and SPR have populations greater than 50% large. FLRW has a high (50%)
percentage of medium host plants. CGI, NPR, CWW, and SPA have no single size greater than 50%. Size
variation may be caused by ecological and observational factors. Tier IVs represent different localized host
plant habitats and require different methods of mapping. Some methods may favor sighting larger bromeliads
(long stretches, trees distant from path, low in density, HPAs few and far between; examples include NPR and
SPR). Shorter, narrower Tier IVs, like CGNRP, with high tree density close to the path, might be more favorable
to sighting all sizes. Those characteristics that determine mapping techniques may play a factor in size
distribution. Such matters will be worked out as the system develops.
Table MRSP-2 begins a breakdown of the host plant population into size, stress value range and species (for
medium and large host plants). This is in need of further work. Similar tables are being created for the Tier IVs.
Graph MRSP-3 shows the number of weevil fallout (dead host plants that fall from the canopy) compared to
the number of weevil evidence (adult, cocoon, pupae or larvae in fallout) found for MRSP. From January to
December 2001 63 fallout and 38 counts of weevil were found in MRSP for a fallout:weevil (FO:W) ratio of 0.6.
Graph 03 shows the fallout-weevil count for Tier IVs. CGR, FLRW, and SPA have no weevil count. CGR and FLRW
just entered the system in December 2001. SPA has maintained grounds and high human activity; fallout may
not remain long on the ground. HC, CGNRP and CGPA have FO:W ratios (0.3 for all three) that are less than that
for MRSP. CGI has a FO:W ratio equal to 0.6, the same as MRSP's. FHR and FLRE have FO:W ratios that are
greater than 0.6, but less than 1.0; and finally, SPR, NPR and CWW have FO:W ratios equal to or greater than
1.0 (1.5, 1.0, and 1.0 respectively).
FLRE had characteristics of a major weevil infestation within a localized host plant patch. SPR and NPR were
brought into the system in December of 2001; weevil evidence was found in single locations for both Tier IVs but
the degree of host plant litter was much less compared to FLRE. All of the fallout and weevil evidence from
CWW came from a single HPA (CWW:Sect-3:HPA-3:hp171, 172 and 173) with three host plants (T. fasciculata,
two large clumps and one medium) that have regularly dropped host plant fallout with weevil evidence. SPR, NPR
and CWW are small, localized areas of devastation. The lifestyle of the weevil makes for scarce evidence. It will
take time and many observations to sort out what the numbers indicate.
Data so far compiled and organized create a baseline description from which suggestive parameters of study
are drawn. So far, this includes recognizing different habitats populated by the host plants, host plant HPA type,
HPA status over time, host plant size and species type, host plant condition over time and modes of
mortality; location of host plant on HPA and relationship to other epiphytes that share the HPA; and number
and location of host plant fallout and weevil count. These parameters will be measured over time and scrutinized
for patterns that may indicate which ecological and observational factors and which biological behaviors are
important to the weevil-host plant interactions. Such patterns will be used for further development of the weevil-
host plant data-analysis system and for making predictions about that system.
At present, no strong conclusions may be drawn, except two. The weevil is entrenched in MRSP and the host
plants are suffering mortality from the weevil. What is not known are the patterns of weevil distribution
and movement or the actual rate of host plant mortality caused by the weevil. Mapping and monitoring is
projected to last three to five years.
A list of links found in this paper may be found at Link List.
Fernald, E.A., Purdum, E.D. 1992. Florida Atlas. University Press of Florida. Gainesville, FL.
Frank, J.H. 2000. Bromeliad Biota. Published on the WWW at http://bromeliadbiota.ifas.ufl.edu.
Frank, J.H., Thomas, M.C. 1994. Metamasius callizona (Chevrolat) (Coleoptera:Curculionidae), an immigrant
pest, destroys bromeliads in Florida. Canadian Entomologist 126:673-682.
Hengeveld, R. 1989. Dynamics of Biological Invasions. Chapman and Hall. London, New York.
Kingsland, S.E. 1985. Modeling Nature. The University of Chicago Press. Chicago.
Larson, B. 2002. Save Florida's Native Bromeliads. Published on the WWW at http://savebromeliads.ifas.ufl.edu/
Myers, R.L., Ewel, J. 1990. Ecosystems of Florida. University of Central Florida Press. Orlando.
Strong, D.R., Lawton, J.H., Southwood, R. 1984. Insects on Plants. Blackwell Scientific Publications. Great Britian.
Winsberg, M.D. 1990. Florida Weather. University of Central Florida Press. Orlando.
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